Process for the manufacture of slewing rings or bearing assemblies

ABSTRACT

A process for manufacturing slewing rings or bearings-rings by centrifugally casting steel to cause the migration of iron particles toward the exterior region of the casting and carbon particles toward the interior region of the casting, and subsequently, quenching the casting to produce a higher degree of hardness to its&#39;&#39; internal region relative to its&#39;&#39; external region and a higher degree of toughness to its&#39;&#39; external region relative to its&#39;&#39; internal region.

United States Patent [191 Dubost 1March 20, 1973 154] PROCESS FOR THEMANUFACTURE OF SLEWING RINGS OR BEARING ASSEMBLIES [75] Inventor:'Jacques Leon Francois Dubost, Ville DAvary, France [73] 'Assignee: R.K. S., Avallon(Yonne), France [22] Filed: Feb. 17, 1971 [21] Appl. No.:116,141

[30] Foreign Application Priority Data Feb. 20, 1970 France ..7006121[52] US. Cl. ..29/148.4 R, 29/1495 R, 29/1592, 29/DIG. 6

[51] Int. Cl. ..B21h 1/12, B2ld 53/10, B23p 17/00 [58] Field of Search..29/148.4 R, 149.5 R, 159.2, 29/527.6, DIG. 6; 164/114 [56] ReferencesCited UNITED STATES PATENTS 1,520,749 12/ l 924 Brownrigg ..164/1 141,781,098 11/1930 Broderick et al.. ..29/D1G. 6 1,908,187 5/1933 Ross..29/159.2 1,987,784 l/l935 McDonald.. ..29/D1G. 6 2,275,503 3/1942Brown ..29/527.6 2,289,703 7/1942 Goerke et a1. ..29/149.5 R

Primary Examiner-Thomas Eager Attorney-Irving M. Weiner [57] ABSTRACT Aprocess for manufacturing slewing rings or bearingsrings bycentrifugally casting steel to cause the migration of iron particlestoward the exterior region of the casting and carbon particles towardthe interior region of the casting, and subsequently, quenching thecasting'to produce .a higher degree of hardness to its internal regionrelative to its external region and a higher degree of toughness to itsexternal region relative to its internal region.

5 Claims, 6 Drawing Figures Pm minmzo ms 3. 720.987

m'vs/v-ran JACQUES LEO/V FRANCOIS M8051 A TTORNEY PROCESS FOR THEMANUFACTURE OF SLEWING RINGS OR BEARING ASSEMBLIES This inventionrelates to the field of metal working.

In lifting equipment, in particular, the rotation of componentsgenerally requires a rotating support which, in the prior art, isprovided by a pivot. More modern designs make use of slewing ring orbearing assembly with incorporated toothing leading to economies fromthe construction and maintenance standpoints.

For such slewing rings, surfaces of great hardness are required for thesupport of the rolling elements, together with a metal of high strengthfor the gear teeth.

The combination of these qualities in a single metal involves verycostly materials.

An object of the present invention is to provide an economic solution tothe problem.

Accordingly, the present invention provides a process for themanufacture of at least one ring of a bearing assembly having externaltoothing, wherein the ring is made in a mold by centrifugal casting,said mold being made to pivot around an axis which is precisely that ofthe ring.

In this manner, as the metal used is steel carbon steel or similar alloyand carbon having a lower density than iron, the centrifugal actionapplied while the metal is still in the liquid or pasty conditionproduces a preferential migration ofthe iron in the region of thetoothing and a concentration of carbon in the region where the rollerpaths are cut.

The regions of the said paths, sufficiently rich in carbon, may beeffectively quenched before grinding so that for the toothing oneobtains a region of high strength and, for the roller paths, a zone ofgreat hardness.

Another object of the invention is a manufacturing process applyingcentrifugal casting, but in which the mold is intended for making atubular element capable of being cut up into a relatively large numberof rings for the same casting operation.

One embodiment of the invention comprises a manufacturing process with amold rotating around a horizontal axis, while another embodimentcomprises a mold rotating around a vertical axis.

In the case of individual casting, which can also be considered, as wellas in the case of multiple ring casting the mold cavities may be given aform such that the corresponding gear teeth have convex flankspermitting a better distribution of contact pressures in the gear teethand a reduction in highly concentrated stresses.

Moreover, the scope of the invention covers all types of gear teeth, aswell as all reliefs, extensions and other shapes, whatever the kind andwhatever the use made thereof, as, for example, attaching lugs, bossesforming cams or other shapes.

turrets, on land or sea, between elements of articulated vehicles, formachine-tools turrets, for handling equipment and for all other similarapplications.

The bearing assemblies thus made are more economical and sturdier thanthose obtained by the conventional means of the art.

The following description of embodiments of such bearing assemblies andof arrangements of mechanisms permitting them to be obtained willprovidea better un' derstanding of the invention and its various advantages.

In the drawing FIG. 1 represents a diametrical section of a bearingassembly, with the external ring appearing in bolder lines than theinternal ring FIG. 2 is schematic representation of a particularembodiment of a horizontal-axis centrifugal casting machine;

FIG. 3 represents a variant of the machine of FIG. 4 shows schematicallya partial section of the differential distribution of carbon in asection of such a ring;

FIG. 5 is a schematic perspective view of the convex shape of the gearteeth which can be thus cast and FIG. 6 represents a diagram for thecasting of a ring with attaching lugs.

As can be seen in FIG. l,a bearing assembly comprises an internal ring 1having perforations 2 for attachment to a support (not shown), saidinternal ring being surrounded by an external ring 3 also provided withperforations 4 for attachment to an element (not shown) which is mobilein relation to the abovementioned support. On its periphery, the ring 3is provided with a toothing 5. The parts opposite these rings may beconnected to each otherby crossed rollers 6 which travel on guide androller paths 7 having a mutual right angle inclination.

As regards the external ring sleeving ring or bearingring 3, accordingto the invention, it is advantageous to produce them by centrifugalcasting. For this purpose and as shown in FIG. 2, one may use acylindrical mold 8 having cavities 9 on its periphery for forming theteeth 5, said mold opening in any desired manner, supported on one sideby a driving pivot 10 in a bearing 11 and, on the other side, by asupport with rollers 12 allowing the clearance of a front opening 13 forthe passage of a nozzle 14 for the liquid metal inlet.

As can be seen in FIG. 3, using certain precautions in the feeding, sucha mold 5 could. be designed in the form of a bowl l5 pivoting around avertical axis and provided with anupper access opening.

In such molds, the casting may be carried out by subjecting the fillingmetal, which is in the form of a tubular body, to the action of a fieldof intensive centrifugal forces, this tubular body then being cut upinto slices each representing the blank of an external ring 3.

In such a blank, it is noted that the carbon steel has ;undergone atransformation which affects its homogeneity. In fact and as shown inFIG. 4, in the zone of the peripheral toothing or teeth 5, the iron icontent has undergone a decrease whereas in the zone :of the internalopening 16, the carbon content has increased. This is due to the factthat the density of lthe patches of carbon is much lower than that ofiron, the latter having a tendency, in the liquid state of the Zmetal,to concentrate on the outside and to drive the ipatches of carboninward.

The consequence of such a manufacturing procedure is that the region ofthe paths 7 are highly carburized whereas the zone of the toothing isless so. Because of this, after quenching, the toughness of thenon-embrittled metal in the zone of the toothing remains very highwhereas the hardness of the metal in the zone of the roller pathsreaches a high value. With a medium carbon steel, one can thusdistinguish the zones which are to undergo working and stresses of aperfectly specialized nature.

This manufacturing process, particularly in the case where such ringsare made individually, makes it possible to provide cavities 9 forproducing teeth a with longitudinally convex flanks 17 as shown in FIG.5. This gives the assurance of a better distribution of loads in thegear teeth contacts. In fact, in this kind of positioning ring gear, thetoothing loads are very high. The convex part of the teeth absorbs, byelastic compression, part of the loads, avoids the risk of breakagewhich could occur under the effect of a bad application, in particularin the marginal regions of the teeth.

Moreover, these teeth obtained by casting have the superiority of beingfree from any scratches which could result from conventional cuttingoperations. The skin of the metal is considerably improved, as well asits surface condition, so that there is no notching effect and the loadcapacity of the teeth is increased.

'In the foregoing illustrative embodiments of the invention, what wasinvolved was the making of gear teeth on the exterior of the ring bycasting, but the principle also applies to other reliefs of the mostvaried kinds. Thus, with reference to FIG. 6 in a mold 18, for example,it is possible to provide cavities permitting the casting of lu'gs'19for the attachment of a ring 20 on any desired support, which lugs canbe cast, by means of suitable cores. directly with perforations used inconjunction with means of attachment, such as bolts,

on the corresponding supports.

Instead of such lugs, it would thus be possible to provide dogs, notchesor other configurations for the most varied uses. In addition, in unitcasting, the lateral faces of the ring could be provided with anydesired reliefs or hollows.

Whatever the configuration of the external reliefs, they have the samequalities of toughness as the gear teeth described above.

It is clear that, without leaving the scope of the invention,modifications are possible in the manufacturing process itself as wellas in the products resulting from its application. Thus, the appellationof steels should be understood to include all iron or carbonbasedalloys. Moreover, all rolling elements, such as balls, rollers, needlesor other elements, could be used.

What is claimed is: l. A process of manufacturing bearing-rings of steelhaving external reliefs, comprising the steps of:

centrifugally casting steel in a ring shaped mold to cause the migrationof the iron particles of the steel toward an internal region of saidbearing-ring being cast to cause a higher carbon content in the internalregion relative to the external region of said bearing-ring; and

quenching said bearing-ring to give a greater degree of hardness to itsinternal region relative to its external region, and a greater. degreeof toughness to its external region relative to its internal re ion dueto the higher carbon content in the mterna region of said bearing-ring.

2. A process as claimed in claim 1, including the additional step ofcentrifugally casting teeth around the external region of saidbearing-ring integral with said bearing-ring.

3. A process as claimed in claim 1, including the additional step ofcentrifugally casting gear teeth around the external region of saidbearing-ring integral with said bearing-ring.

4. A process as claimed in claim 1, including the additional step ofcentrifugally casting gear teeth having longitudinally convex flanksaround the external region of said bearing-ring integral with saidbearing-ring.

5. A process as claimed in claim 1, including the additional step ofcentrifugally casting a series of reliefs having the form of attachmentlugs around the external surface of said bearing-ring integral with saidbearingring.

1. A process of manufacturing bearing-rings of steel having externalreliefs, comprising the steps of: centrifugally casting steel in a ringshaped mold to cause the migration of the iron particles of the steeltoward an internal region of said bearing-ring being cast to cause ahigher carbon content in the internal region relative to the externalregion of said bearing-ring; and quenching said bearing-ring to give agreater degree of hardness to its internal region relative to itsexternal region, and a greater degree of toughness to its externalregion relative to its internal region due to the higher carbon contentin the internal region of said bearing-ring.
 2. A process as claimed inclaim 1, including the additional step of centrifugally casting teetharound the external region of said bearing-ring integral with saidbearing-ring.
 3. A process as claimed in claim 1, including theadditional step of centrifugally casting gear teeth around the externalregion of said bearing-ring integral with said bearing-ring.
 4. Aprocess as claimed in claim 1, including the additional step ofcentrifugally casting gear teeth having longitudinally convex flanksaround the external region of said bearing-ring integral with saidbearing-ring.
 5. A process as claimed in claim 1, including theadditional step of centrifugally casting a series of reliefs having theform of attachment lugs around the external surface of said bearing-ringintegral with said bearing-ring.